Separation of ethylbenzene from para- and meta-xylenes by extractive distillation

Abstract

Ethylbenzene and para-xylene and/or meta-xylene are difficult to separate by distillation because they boil only 2.3 C.° and 3.1 C.° apart. Ethylbenzene can be readily separated from the xylenes by using extractive distillation in which the extractive distillation agent is a mixture of oxygen-containing organic compounds boiling higher than the xylenes. The mixture typically includes phthalic anhydride and maleic anhydride with or without a solvent.

The nature of the present invention having been described and illustrated, what I wish to claim as new and useful and secure by Letters Patent is: 
     
       1. A method for the separation of ethylbenzene from p-xylene and/or m-xylene which comprises distilling a mixture of ethylbenzene and p-xylene and/or m-xylene in the presence of an effective amount of an extractive agent comprising a mixture of phthalic anhydride and maleic anhydride. 
     
     
       2. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride, maleic anhydride and one of the following; Acetonylacetone, Acetphenone, Acetyl salicylic acid, Adiponitrile, p-tertiary Amyl phenol, Anisole, Azelaic acid, Benzaldehyde, Benzoic acid, Benzonitrile, Benzophenone, Benzyl acetate, Benzyl alcohol, Butoxypropanol, Butyl benzyl phthalate, o-secondary Butyl phenol, 2-tertiary Butyl phenol, 3-tertiary Butyl phenol, 4-tertiary Butyl phenol, 1,3-Butylene glycol, beta-Butyrolactone, Carbitol acetate, Citronellyl acetate, m-Cresol o-Cresol, Cuminaldehyde, Cyanoacetic acid, Decanoic acid, Dibenzofuran, 2,6-di-tertiary Butyl-p-cresol, Dibutyl ether, 2,5-di-tertiary Butyl hydroquinone, 2,6-di-tertiary Butyl phenol, Diethyl maleate, Diethyl malonate, Diethyl phenyl malonate, Diethyl phthalate, Diethyl succinate, Diethylene glycol butyl ether acetate, Diethylene glycol dimethyl ether, Diethylene glycol methyl ether, Dihydroterpinyl acetate, Diisobutyl ketone, Dimethyl formamide, 3,5-Dimethyl phenol, Dimethyl succinate, Dimethyl sulfone, Dimethyl sulfoxide, Ethyl acetoacetate, 2-Ethyl butyric acid, 2-Ethylhexanol, Ethyl hexyl acetate, Ethyl phenyl acetate, Ethyl salicylate, p-Ethyl phenol, Ethylene glycol butyl ether, Ethylene glycol ethyl ether acetate, Ethylene glycol mono stearate, Fenchyl alcohol, 9-Fluorenone, 1,6-Hexanediol, Hexahydrophthalic acid anhydride, Hexyl acetate, Hexylene glycol, Hexylene glycol diacetate, Hydro bis phenol A, Isoborneol, Isobornyl acetate, Isobornyl methyl ether, Isooctanol, Isophorone, Isopropyl myristate, Linalyl acetate, Menthyl acetate, Methyl benzoate, 4-Methyl benzophenone-2-carboxylic acid, Methyl hexanoate, Myristic acid, m-Nitroacetophenone, p-Nitroacetophenone, m-Nitrobenzaldehyde, m-Nitrobenzoic acid, 5-Nitroisophthalic acid diethyl ester, p-Nitrophenol, p-Nitrophenylacetic acid, p-Nitrotoluene, Nonanic acid, 2-Octanone, Phenethyl alcohol, Phenol, Phenyl acetate, Phenyl acetic acid, 2-Phenylphenol, 3-Phenyl-1-propanol, Propionic anhydride, Propoxypropanol, Propyl-p-hydroxybenzoate, Sebacic acid,, Succinic anhydride, Succinimide, Sulfolane, Sulfolene, Tetrahydrofurfuryl alcohol, 2,2',4,4'-Tetrahydroxybenzophenone, p-Tolualdehyde, Tributylphosphate, Triethylene glycol diacetate, o-Toluic acid. 
     
     
       3. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride and benzoic acid. 
     
     
       4. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride, benzoic acid and one of the following; Diisononyl phthalate, Diethylene glycol ethyl ether acetate, Methyl salicylate, Diisobutyl ketone, Diisononyl phthalate, Diisobutyl phthalate, Diethyl maleate, Methyl hexanoate, Isobutyl isobutyrate, Dimethylsulfoxide, Dimethylformamide, n-Octanol, n-Decanol, Ethyl acetoacetate, 4-Nitrophenol, 4-tertiary Butyl phenol, Dimethylsulfone, 4-tertiary Butyl catechol, 2-Phenylphenol. 
     
     
       5. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride, salicylic acid and one of the following; Diisobutyl phthalate, Methyl hexanoate, Ethylene glycol phenyl ether, and the pair Dimethylsulfoxide, Methyl hexanoate. 
     
     
       6. The process of claim 1 in which the extractive distillation agent comprises a mixture of benzoic acid, maleic anhydride and one of the following; Diethyl maleate, Methyl hexanoate, Acetophenone, Triethylene glycol diacetate, Diethylene glycol hexyl ether, Dimethyl phthalate, Dibutyl phthalate, Diisononyl adipate, Tributyl phosphate, n-Octanol, 1,6-Hexanediol, 4-secondary Butyl phenol, p-Ethylbenzaldehyde. 
     
     
       7. The process of claim 1 in which the extractive distillation agent comprises a mixture of benzoic acid, maleic anhydride, phthalic anhydride and one of the following; Glycerol triacetate, Diethyl maleate, Phenyl acetate, Ethylene glycol diacetate, Dimethyl adipate, Ethylene glycol methyl ether acetate, Diethylene glycol diethyl ether, Tributyl phosphate, Tricresyl phosphate, Catechol, Ethyl acetoacetate, Phenol, o-Cresol, 2,6-Dibutyl phenol, Diisobutyl ketone, Tetrahydrofurfuryl alcohol. 
     
     
       8. The process of claim 1 in which the extractive distillation agent comprises a mixture of maleic anhydride and one of the following pairs; m-Nitrobenzoic acid & Butoxypropanol, 4-tertiary Butyl catechol & Nonanic acid, 2-Phenylphenol & Isobornyl acetate, p-Nitrophenol & Myristic acid. 
     
     
       9. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride and one of the following; Levulinic acid, m-Nitrobenzoic acid, Acetonylacetone. 
     
     
       10. The process of claim 1 in which the extractive distillation agent comprises a mixture of phthalic anhydride and one of the following pairs; Acetylsalicylic acid & Isophorone, Azelaic acid & Isophorone, o-Toluic acid & Phenol. 
     
     
       11. The process of claim 1 in which the extractive distillation agent comprises a mixture of hexahydrophthalic anhydride, maleic anhydride and one of the following; Butoxypropanol, n-Octanol. 
     
     
       12. The process of claim 1 in which the extractive distillation agent comprises a mixture of maleic anhydride, azelaic acid and one of the following; Ethylphenyl acetate, Phenylacetic acid. 
     
     
       13. The process of claim 1 in which the extractive distillation agent comprises a mixture of Phthalic anhydride, Benzoic acid, Dimethylsulfoxide and Methyl hexanoate. 
     
     
       14. The process of claim 1 in which the extractive distillation agent comprises a mixture of Phthalic anhydride, Succinic acid, Ethylene glycol diacetate and Carbitol acetate. 
     
     
       15. The process of claim 1 in which the extractive distillation agent comprises a mixture of Benzoic acid, Succinic anhydride and Diethyl maleate. 
     
     
       16. The process of claim 1 in which the extractive distillation agent comprises a mixture of Phthalic anhydride, Methyl p-hydroxybenzoate and Diethyl oxalate. 
     
     
       17. The process of claim 1 in which the extractive distillation agent comprises a mixture of Benzoic acid, Salicylic acid and Tributyl phosphate. 
     
     
       18. The process of claim 1 in which the extractive distillation agent comprises a mixture of Maleic anhydride and m-Nitroacetophenone.